Color filters used in liquid crystal display devices are equipped with a light shielding film called black matrix, for the purpose of shielding light among colored pixels and enhancing the contrast. Furthermore, solid-state imaging devices are also provided with a black matrix for the purpose of preventing generation of noise, enhancing the image quality, and the like. A black matrix is produced by preparing a polymerizable composition that includes a polymerizable composition in which a black coloring material having light shielding properties is dispersed, a polymerizable compound, a polymerization initiator and other components, and forming a pattern with the polymerizable composition.
As the composition for forming a black matrix for liquid crystal display devices or solid-state imaging devices, photosensitive resin compositions containing a black coloring material such as carbon black or titanium black are known.
Black matrices for liquid crystal display devices needs to have high light shielding properties in order to increase the contrast and enhance the visibility. On the other hand, black matrices for solid-state imaging devices needs to have light shielding properties with respect to light in the visible region, in addition to light shielding properties in the infrared region.
Conventional light shielding color filters that form light shielding black matrices have mainly used carbon black. However, there has been a problem in that if the filling amount of carbon black is increased for the purpose of increasing the light shielding properties, it becomes difficult to disperse carbon black and deteriorates pattern formability.
While there is a demand for further miniaturization of black matrices for liquid crystal display devices, black matrices for solid-state imaging devices (in particular, black matrices formed on the surface of a support opposite to the side on which light-receiving devices are formed (hereinafter, also referred to as “back surface”) need to have an ability of uniformly shielding light in a larger area, as compared with black matrices for liquid crystal display devices.
Furthermore, when a light shielding film having a large area is formed as a light shielding film for solid-state imaging devices by using a conventional photosensitive resin composition, there may be a case of forming a region in a peripheral portion in which the thickness of the light shielding film is smaller than the thickness at the central part of the light shielding film (steps), whereby the light shielding ability at the peripheral part of the light shielding film may decrease.
In response to the requirements for product quality of black matrices with high light shielding properties as described above, titanium black, which exhibits high light shielding properties, has become very useful, and various methods have been proposed in order to improve the dispersibility of titanium black (see Japanese Patent Application Laid-Open (JP-A) No. 10-246955, JP-A No. 9-54431, JP-A No. 10-46042, JP-A No. 2007-115921, JP-A No. 10-114836, JP-A No. 2002-275343, and JP-A No. 2005-266189). However, since titanium black has a large specific gravity, it is more difficult to disperse titanium black as compared with carbon black, and problems such as precipitation over time are prone to occur. Therefore, when forming a uniform light shielding color filter using titanium black, there is a demand for a material that achieves favorable dispersibility and dispersion stability of titanium black, and is capable of forming a favorable light shielding pattern with high sensitivity.
Furthermore, in recent years, imaging units having a small size and reduced thickness are used in portable terminals of electronic instruments such as mobile phones or personal digital assistants (PDAs). Such imaging units normally include a solid-state imaging device such as a charge coupled device (CCD) image sensor or a complementary metal-oxide semiconductor (CMOS) image sensor, and a lens for forming a subject image on the solid-state imaging device.
As the size or the thickness of mobile terminals decreases, there is a demand for reducing the size or the thickness of imaging units. Further, in order to reduce the production costs for mobile terminals, streamlining of production processes is desired. As a method for producing a large number of small lenses, a method of mass producing lens modules is known in which a wafer-level lens, formed from a support and plural lenses provided on the support, is cut and separated into plural lenses.
Further, a method of mass producing imaging units is known in which a support on which plural lenses are formed and a sensor support on which plural solid-state imaging devices are formed are assembled, and the sensor support is cut together with the support such that a set of a lens and a solid-state imaging device is included therein.
Conventionally, in regard to wafer-level lenses, for example, a constitution of a multilayer wafer-level lens formed by layering supports each having plural lenses formed thereon is known (see, for example, Japanese Patent Application National Publication (Laid-Open) No. 2005-539276). Further, a method of obtaining a wafer-level lens by supplying a material for forming lenses on a support, and forming lenses on the support using a mold, is known (see, for example, WO 2007/107025). It is important also for such wafer-level lenses to form suitable light shielding films.